Choose your material by finding rocks in nature or using landscaping stones.  You want to use ones that are fairly flat on one side.  Keep in mind that the settings in the file work best for rocks with a red or brown tone.  If you choose another color such as gray, you may want to do a test to determine the best settings.  Rinse your rocks to get off any dirt.  

Choose the image you want to engrave on your stone and copy and paste into canvas2.  Place your stone on your honeycomb with the flattest side up.  Use scrap material and/or honeycomb pins to make the top as level as possible and keep the rock from moving.  Use the auto measure and mark your processing area using the polygon.  Move your image inside your marked area.  You may need to resize and/or rotate as needed.

Process your image.  When it's finished, you can choose to spray a clear coat of polyurethane to give it a little more contrast and shine.  Now you can place your stones wherever you desire.